Organic film formation is an essential step in manufacturing OLED displays. Generally, organic films of OLED devices have to have a uniform and thin thickness. Therefore, it is challenging for any person skilled in the art to form an organic film that is thin and, in the meanwhile, has a uniform thickness.
One organic film formation technique is to use a fine metal mask (FMM) to form organic films by vacuum evaporation. Such technique using FMM includes step of heating an organic material under vacuum, so as to have organic material be evaporated and deposited on substrate on which a mask is disposed, such that a sub-pixel film is formed in corresponding areas on the substrate. Although the FMM technique has been widely used, alignment between mask and substrate is still not precise because mask itself will deform due to gravity and thermal expansion thereof, and thus organic film cannot be accurately and efficiently formed.